U.S. patent number 5,171,278 [Application Number 07/659,758] was granted by the patent office on 1992-12-15 for middle expandable intervertebral disk implants.
Invention is credited to Madhavan Pisharodi.
United States Patent |
5,171,278 |
Pisharodi |
December 15, 1992 |
Middle expandable intervertebral disk implants
Abstract
Artificial disk implant and methods for implanting it, the
implant having a member for adapting in size and shape to an
anatomical space between vertebrae and apparatus for expanding the
member to conform to the space.
Inventors: |
Pisharodi; Madhavan
(Brownsville, TX) |
Family
ID: |
24646707 |
Appl.
No.: |
07/659,758 |
Filed: |
February 22, 1991 |
Current U.S.
Class: |
128/898; 606/279;
623/17.16; 606/247 |
Current CPC
Class: |
A61F
2/446 (20130101); A61F 2/4455 (20130101); A61F
2/442 (20130101); A61F 2002/30329 (20130101); A61F
2230/0017 (20130101); A61F 2002/30451 (20130101); A61F
2002/30594 (20130101); A61F 2230/0069 (20130101); A61F
2002/30146 (20130101); A61F 2002/30471 (20130101); A61F
2220/0058 (20130101); A61F 2002/30293 (20130101); A61F
2002/30113 (20130101); A61F 2002/30624 (20130101); A61F
2230/0091 (20130101); A61F 2002/30405 (20130101); A61F
2002/30556 (20130101); A61F 2002/30573 (20130101); A61F
2002/30579 (20130101); A61F 2002/30153 (20130101); A61F
2220/0041 (20130101); A61F 2002/3028 (20130101); A61F
2002/30777 (20130101); A61F 2230/0019 (20130101); A61F
2002/30224 (20130101); A61F 2002/2835 (20130101); A61F
2310/00023 (20130101); A61F 2002/30433 (20130101); A61F
2002/30787 (20130101); A61F 2230/0021 (20130101); A61F
2002/30225 (20130101); A61F 2002/30235 (20130101); A61F
2002/30599 (20130101); A61F 2230/0006 (20130101); A61F
2250/0009 (20130101); A61F 2002/30507 (20130101); A61F
2250/0063 (20130101); A61F 2210/0014 (20130101); A61F
2/30744 (20130101); A61F 2220/0025 (20130101); A61F
2230/0082 (20130101); A61F 2002/30092 (20130101); A61F
2002/30143 (20130101); A61F 2002/30261 (20130101); A61F
2230/0063 (20130101); A61F 2002/30154 (20130101) |
Current International
Class: |
A61F
2/44 (20060101); A61F 2/00 (20060101); A61F
2/02 (20060101); A61F 2/28 (20060101); A61F
2/30 (20060101); A61F 002/44 () |
Field of
Search: |
;623/17,16,18
;606/60,61,63 ;128/69 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2701279 |
|
Jul 1977 |
|
DE |
|
3729600 |
|
Mar 1989 |
|
DE |
|
2639823 |
|
Jun 1990 |
|
FR |
|
0662082 |
|
May 1979 |
|
SU |
|
0906548 |
|
Feb 1982 |
|
SU |
|
1122304 |
|
Nov 1984 |
|
SU |
|
Primary Examiner: Green; Randall L.
Assistant Examiner: Willse; D.
Attorney, Agent or Firm: Vaden, Eickenroht, Thompson,
Boulware & Feather
Claims
I claim:
1. A method of implanting an intervertebral disk unit between two
vertebrae after removal of a diseased or damaged intervertebral
disk from therebetween, the disk unit being cylindrical in shape
and comprising a member capable of adapting to the shape of an
anatomical region of said disk space and means for variably
expanding said member to substantially conform the shape of said
member to the shape of a portion of said disk space, comprising the
steps of:
(a) inserting said disk unit into said disk space;
(b) expanding the middle of said disk unit without changing the
diameter of the dimensions of the ends thereof; and
(c) introducing cancellous bone particles into said disk space and
allowing said particles to fuse.
2. The method of claim 1, further comprising:
contacting an adhesive substance medially to said disk unit to
close off the disk space.
3. The method of claim 1, wherein said cancellous bone particles
are introduced into said disk space medial to the disk unit.
4. A method of implanting an artificial intervertebral disk unit
between two vertebrae after removal of a diseased or damaged
intervertebral disk, the disk comprising a rectangular member
comprised of a plurality of rectangular subunits including
interconnected end and intermediate subunits, capable of adapting
to an anatomical region of a disk space and means for variably
moving the intermediate rectangular subunits so that said implant
conforms to anatomical boundaries of the disk space, comprising the
steps of:
(a) inserting said disk unit into said disk space; and
(b) expanding said disk unit, wherein said means for moving the
intermediate subunits includes screw means threadedly received in
the end subunits.
5. The method of claim 4, further comprising:
tightening lock nut means against said screw means to prevent
movement of said intermediate subunits.
6. A method of implanting an artificial intervertebral disk unit
between two vertebrae after removal of a diseased or damaged
intervertebral disk, the disk unit comprising a member capable of
adapting to an anatomical region of a disk space and means for
variably expanding said member to allow said member to
substantially conform to a portion of said disk space, comprising
the steps of:
(a) inserting said disk unit into said disk space;
(b) expanding said disk unit;
(c) introducing cancellous bone particles into said disk space;
and
(d) contacting an adhesive substance medially to said disk unit to
close off said disk space.
7. A method of implanting an intervertebral disk unit between two
vertebrae after removal of a diseased or damaged intervertebral
disk from therebetween, the disk unit being rectangular in shape
and comprising intermediate and end subunits forming a member
capable of adapting to the shape of an anatomical region of said
disk space and means for variably expanding said member to
substantially conform the shape of said member to the shape of a
portion of said disk space, comprising the steps of:
(a) inserting said disk unit into said disk space;
(b) expanding the intermediate subunits comprising the middle of
said disk unit without expanding the subunits comprising the ends
thereof; and
(c) introducing cancellous bone particles into said disk space and
allowing said particles to fuse.
8. The method of claim 7, wherein said cancellous bone particles
are introduced into said disk space medial to the disk unit.
Description
RELATED APPLICATION
Filed on even date herewith is Applicant's application entitled
Artificial Spinal Prosthesis, a copy of which is submitted
herewith
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an artificial intervertebral disk
implant. More particularly, the present invention relates to
cylindrical and rectangular disk implants which are expandable in
the middle and can be used alone or in various combinations for the
purpose of spinal fusion.
2. Description of the Related Art
The spine is a flexible structure comprised of thirty-three
vertebrae. The vertebrae are separated and cushioned from each
other by fiber cartilage in structures called intervertebral disks.
If the spine is injured or becomes diseased, these disks are
surgically removed. Such disk injuries can happen in the neck, in
the thoracic region and in the lumbar region. The more frequent
injuries are in the lower lumbar and in the lower cervical
regions.
Treatment of herniated disk in the neck and in the lumbar region
continues to be a challenging field of medicine. The classical
treatment for a ruptured disk continues to be removal of the disk
which is normally needed between the vertebrae. In the process, a
defect is made which continues to bother the patients throughout
the rest of their life. One additional procedure previously
attempted is to replace the disk space with a bone graft, thus,
bringing about a spinal fusion, i.e. a fusion of the two vertebrae
thus eliminating the empty space between the vertebrae.
Theoretically, this is a satisfactory procedure, though not ideal
because the replaced bone does not have any of the functions of the
cartilage tissue, i.e. no cushioning effect. This procedure,
however, is technically demanding and has medical complications
because of several physiological factors. First of all, the bone
plug used to pack the disk space does not conform to the shape of
the disk because the disk bulges maximally in the center. The disk
space is wider in the middle and narrow at its anterior and
posterior ends. It is impossible to insert a bone plug having its
maximum width at the center because it cannot be inserted through
the mouth of the disk space. For this reason, the various bone
plugs have only four point contacts, i.e. at the front and back
part of the disk space. Secondly, if the bone pieces do not fuse
within a minimum period of time, they dissolve, become thinner and
many eventually extrude out of the disk space, causing pressure on
the nerve roots.
Various synthetic disk plugs have been proposed in the past, but
all have the problem of not conforming to the shape of the disk
space. There has long been a need for a disk plug capable of
supporting the disk space after a simple diskectomy.
SUMMARY OF THE INVENTION
A synthetic intervertebral disk implant is described for
implementation into the disk space after surgical removal of a
diseased or damaged intervertebral disk. Implants according to this
invention have a member for adapting to the anatomical region of
the disk space and apparatus for expanding the member so it
conforms to a portion of that space.
In one preferred embodiment, there is provided an artificial
intervertebral disk implant having a cylindrical body comprised of
cylindrical subunits capable of expansion. In another preferred
embodiment, there is provided an artificial intervertebral disk
implant having a rectangular body comprised of rectangular subunits
capable of expansion. Both the cylindrical and rectangular implants
are disk plugs expandable in the middle portion to provide contact
with substantially the entire area of the disk space against the
vertebral bodies.
The present invention recognizes and addresses the
previously-mentioned long-felt needs and provides a satisfactory
meeting of those needs in its various possible embodiments. To one
of skill in this art who has the benefits of this invention's
teachings and disclosures, other and further objects and advantages
will be clear, as well as others inherent therein, from the
following description of presently-preferred embodiments, given for
the purpose of disclosure, when taken in conjunction with the
accompanying drawings. Although these descriptions are detailed to
insure adequacy and aid understanding, this is not intended to
prejudice that purpose of a patent which is to claim an invention
no matter how others may later disguise it by variations in form or
additions of further improvements.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above cited features, advantages,
and objects of the invention as well as others which will become
clear are attained and can be understood in detail. More particular
description of the invention briefly summarized above may be had by
reference to certain embodiments thereof which are illustrated in
the appended drawings, which drawings form a part of the
specifications. It is to be noted, however, that the appended
drawings illustrate preferred embodiments of the invention and are
therefore not to be considered limiting of its scope for the
invention may admit to equally effective equivalent
embodiments.
In the accompanying drawings FIG. 1 is a side elevation view of the
cylindrical disk implant.
FIG. 2 is a side elevation view of an expanded cylindrical disk
implant.
FIG. 3 is a cross section view of the implant.
FIG. 4 is a side elevation view of the rectangular disk
implant.
FIG. 5 is a side elevation view of an expanded rectangular disk
implant.
DETAILED DESCRIPTION OF THE INVENTION
The disk implants of the present invention can be understood with
FIGS. 1 to 5 in which the numerals represent like parts. FIG. 1
depicts a cylindrical embodiment of the present invention. A disk
implant 20 is comprised of a strong thin non-porous material.
Suitable materials for the disk implant 20 include, modified
carbon, titanium, steel, any surgical implant material or any
biologically compatible material. The disk implant 20 is comprised
of a plurality of subunits 22, 24 and 26 as screw 28 may be turned
to cause expansion of subunits 24 and 26. The expanded shape of the
disk implant 20 is shown in FIG. 2. Turning screw 28 allows for
maximal expansion of the subunit 26 and moderate expansion of the
subunit 24.
Turning of Phillips screw 28 expands subunits 24 and 26 which
remain in an expanded shape due to the lock nut 21. Removal of lock
nut 21 is accomplished by turning of the allen screw 30 which holds
lock unit 21 to subunit 22.
Lock nut 21 is inlaid into end subunit 22 and is fixed by the allen
screw. Lock nut 21 is removed if the implant has to be removed.
FIG. 2 illustrates a cross section of the disk implant 20. By
adjusting the diameter of the screw shaft (not pictured) and
thickness of the cylindrical sheets, the subunits 24 and 26 can be
expanded as desired. The cylindrical disk implant 20 is expanded as
the sheets 32 are uncoiled. Generally, any method that allows for
expansion of either embodiment of the disk implant may be used. For
the cylindrical disk implant, turning the screw uncoils the sheets
because the inside end of the sheet is attached to the screw.
FIG. 3 illustrates the cylindrical disk implant in its expanded
form. In its expanded form, the implant cannot be removed from the
disk space.
FIG. 4 depicts a rectangular disk implant 31 according to the
present invention. Turning Phillips head 39 of screw 42
encapsulated in a sheet 44 allows rotation of a hinge 38 of
intermediate subunits 34 superiorly and rotation of inferior
intermediate subunits 36 inferiorly. In the rectangular implant,
subunits 32 are not mobile. The expanded shape of the rectangular
disk plug 31 is illustrated in FIG. 5. Intermediate parts 34 and 36
are secured to an end part 32 by hinge 38. Intermediate parts 34
and 36 are secured to each other by hinge 46. Lock nut 40 is
inserted over Phillips screw head 39. Lock nut 40 prevents the
subunits from moving from the expanded shape. Removing lock nut 40
allows subunits 34 and 36 to uncoil.
The cylindrical and rectangular implants can be inserted after a
simple diskectomy. Ordinarily, the size of the disk implant will be
approximately 2.5 to 3.5 centimeters in length and 1.0 to 1.5
centimeters in height and width.
These disk implants are expandable in the middle portion so as to
contact substantially the entire anterior-posterior length of the
disk space against the vertebral bodies. If a complete
intervertebral fusion is desired, this plug can be used in
conjunction with intervertebral cancellous bone packing. Because of
the support provided by the plug, in the initial stages until the
fusion is established, the cancellous bone pieces have a better
chance of fusion and also it has a better chance of staying in the
intervertebral disk space. Alternately, the intervertebral disk
plug can be used to maintain the disk height and this plug can be
used in conjunction with intertransfers posterior lateral fusion.
In short, this plug, which can be expanded in the middle, is going
to act as a physiological support for the rest of the patient's
life or until a bone fusion is established.
The disk implants of the present invention may have additional
indications, e.g. short segment scoliosis where the curvature of
the spine can be corrected by distracting the vertebral bodies on
the inside of the curvature. By expanding the plugs inside the disk
space the vertebral bodies are distracted and this can help
straighten the spinal column.
If no bone graft is being planned it is recommended that the
diskectomy be made minimally through one side exposures so that
when the disk plug is inserted and expanded, it will take the empty
room in the space. Because there is no further movement at this
disk space, the chance of recurrent disk herniation will be
minimized. Also the recurrent disk herniation is due to the opening
and closing effect of the disk space towards the side where
diskectomy is done and since the disk plug closed this mouth, the
mouth cannot be opened and closed. By doing this process, in
addition to one sided simple diskectomy, the risk of recurrent disk
herniation can be reduced.
Two preferred types of disk plugs are proposed: one is rectangular
and the other one is cylindrical. Both have the common feature of
being expandable in the middle without changing the diameter of the
dimensions of the two ends. The surgery is performed as in simple
diskectomy and through a small laminotomy the disk is exposed. The
disk material is removed and the nerve root compression is
corrected. The posterior longitudinal ligament and disk cartilage
are removed until the vertebral surfaces are exposed above and
below the disk space. Depending upon the disk plug used, the disk
space is fashioned either cylindrically or in a rectangular
fashion. The disk plug is then inserted and hammered into place so
that the anterior end of the disk plug will be almost touching the
anterior longitudinal ligament. Subsequently, using a Phillips
screw driver, the posterior screw end is turned. This also gives a
good distraction to the vertebral bodies. In simple disk problems
no further treatment is required.
When used alone without bone grafts, these disk implants should
reduce the possibility of recurrent disk herniations. This is
accomplished by a decrease in the mobility of the disk and the
decrease in the disk mouth space.
If, however, an interbody fusion is desired, cancellous bone chips
are made into very fine particles and pumped into the disk space
medial to the disk plug and packed into the space. The posterior
longitudinal ligament is intact to the opposite side and to the
center of the disk space. These cancellous bone chips are held
tightly in place. Since the mouth of the disk space is closed with
the disk plug, the risk of the cancellous bone chips coming out is
minimized. Also, the disk plug will prevent opening and closing of
the disk space, thus preventing the bone chips coming out. If
necessary, a small amount of glue can be applied over the
cancellous bone chips just medial to the disk plug to close off the
remaining portion of the opening of the disk space. The patient
should be able to ambulate soon after the surgery because of the
stability given by the disk plug. Before narrowing of the disk
space occurs, the cancellous bone chips will have started the
fusion process.
If on the other hand, the posterior lateral intertransverse fusion
is desired, this procedure may be done in conjunction with the
middle expandable disk plug. The disk plug is applied as explained
above and then the surgeon does the posterior lateral fusion. Since
the disk plug provides stability to the spine until the posterior
lateral fusion is solid, the patient can ambulate soon after the
surgery. Also this prevents the disk space narrowing which is a
common problem with posterior lateral fusion.
The disk plugs can be made of any suitable material including a
material like modified carbon so that they will be magnetic
resonance imaging (mri) compatible. This is a simple and safe
procedure with a wide range of applications in the management of
low back pain. The same plug in smaller dimensions can be used in
thoracic and cervical levels where indicated. In the neck this can
be used following the anterior cervical diskectomy without the risk
of the plug migrating anteriorly or posteriorly.
There is provided in preferred embodiments an artificial
intervertebral disk implant having a cylindrical body comprised of
cylindrical coils capable of expansion and intervertebral disk
implant having a rectangular body comprised of rectangular blocks
capable of expansion in the middle. Both the cylindrical and
rectangular implants are disk plugs being expandable in the middle
portion so as to provide contact with substantially the entire
anterior posterior length of the disk space against the vertebral
bodies.
The present invention recognizes and addresses the previously
mentioned long felt needs and provides a satisfactory meeting of
those needs in its various possible embodiments. To one of skilled
in this art who has the benefits of this inventions teachings and
disclosures other and further objects and advantages will be clear
as well as others inherit their end from the following description
of presently preferred embodiments given for the purpose of
disclosure when taken in conjunction with the accompanying
drawings. All those descriptions are detailed to insure an aid in
understanding. This is not intended to prejudice the purpose of a
patent which is to claim an invention no matter how others may
later disguise it by variations in form or additions are further
improvements.
* * * * *